1979 Dodge Van Engine runs fine, then not at all

318 v8 2bbl, AT. Pump pedal 2-3 times, set choke and starts ok if not sitting for months (I don't drive this much if months then I pump it a lot). Let fully warm up and drive 6-7 mi. Ok, does not stall, will accelerate, including foot to the floor ok but after 6 to 7 miles if then slow down in trafic and truck begins to idle slower and wants to die, blipping the gas in neutral will not help-it dies. It struggles and dies as if it were running out of gas but I ran it with air cleaner off today and the accelerator pump was still squirting gas, so gas not problem. Trying to restart, it cranks freely but with no hint of starting. But wait 10 minutes or so when it is in a good mood and it will start with 2 to 3 pumps of gas pedal. Plugs, cap, rotor and wires within the last 2K mi, fuel pump, fuel filter, carb fuel level seems ok. Sprayed base of carb with water while running to check leaks no change, shook carb no change, and blocked carb air horn while running and it did start to die, so no vacuum leak?

Is there something electrical that could die on the truck when it gets hot and then come back on cooling, like a spark module or something?

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Thursday, September 10th, 2009 AT 7:27 PM

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ARTHUR1920

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Got it to do it again today on purpose.

Low speed driving no problem. Then out on intermediate highway, a couple of bursts up to 50. Same route that caused the failure before. And 5 to 6 mi later, slowed down at an intersection and it started to shudder, and idle down. Shifted to neutral and tapped the gas but it still died. Turned over good but no hint of starting. Thought ahah.I bet there is no spark. Pulled a plug wire and yes I did have spark. Then I noticed wetness at the base of the carb gasket. Lots of white smoke comes out of carb.I figure this is gas in the manifold vaporizing?

So it's not lack of spark.
It not clogged fuel line because when it does this I look in the carb and press the gas and the accelerator pumps still squirts, so there must be gas in the float bowl.

Vacuum gauge is 19 mm at slow idle and 21 at 1st fast idle step, revving and holding, vac drops but then climbs back to 21.

Could I have a sinking float?

Anyway after I waited a few minutes then the van started up. Repeated the stall-wait-restart once more on way home. Made it home turned van off in drive and watched. White smoke and wetness at base of carb.

What do you think?

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Saturday, September 12th, 2009 AT 6:34 PM

ARTHUR1920

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OK,
after many trips to repair shop:

Rebuilt carb and replace intake manifold gasket (I think the gasket was fine) carb may have had sinking float or sticking needles.

Swap ign. Module in and out-no change.

Mechanic said the "one way valve" in the fuel line was defective. No change.

On test drives truck continued to starve out going up hill.

I finally put a 5 gal. Can of gas on the pass seat and ran a line under the truck to where the filter was. Then the truck ran fine.

So, I was finally able to get the mechanic to listen to me when I said the problem had to be between the fuel filter and the gas tank. He took down the tank and said the lines were bad. Replaced the lines and now the truck will run up hill.

It's still not the greatest running truck but it never was since new always felt lean on part throttle especially when it was shifting 1 to 2. 1979 was a lousy year for smog equipped vehicles. But at least now I can run up hill flat out without it cutting out and stopping.

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Friday, November 20th, 2009 AT 4:13 PM

DOCFIXIT

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Think problem was debris in tank cloging up pickup sock starving engine. When it dies suction lost at sock debris falls off. Restart runs till it cloges up again.

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Friday, November 20th, 2009 AT 4:25 PM

ARTHUR1920

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Replacing the lines on the OUTSIDE of the gas tank, on top of the tank, solved the problem without going inside looking for debris. At least, so far.